By default, the ftp command may not be installed on your system. apt-get or yum can be used to install the ftp command.

apt-get install ftp
yum install ftp

To connect to a FTP server, at the command line, type FTP and then the domain name or IP address of the FTP server.  If there is only a prompt such as FTP >, you are not connected to the FTP server.

ftp 192.168.0.77
ftp>

On the other hand, after typing ftp and then the domain name or IP address of the FTP server, if you get a welcome message, you are connected to the FTP server.

ftp 192.168.0.23
Connected to 192.160.0.77
220---------Welcome to Pure-FTPd [privsep] [TLD]---------
220-You are user number 1 of 50 allowd.
220-Local time is now 20:37.  Server port: 21.
220-This is a private system - No anonymous login
220-IPv6 connections are also welcome on this server.
220-You will be disconnected after 15 minutes of inactivity.
User (192.168.0.77:(none)):

You will now need to issues commands to be authenticated.  Type user and then your username.  Next type your password.

User (192.168.0.77:(none)): billyt
331 User billyt OK.  Password required
Password: ********
230 OK. Current directory is /
ftp >

You are now connected, and you can use typically commands such as PWD and CD and LCD.  The most common first task is to upload a file to the remote computer.

ftp> LCD C:\ 
#Local change directory
ftp> PUT *   
#Transfer everything in the LCD to the remote machine

Use the quit command to disconnect from the FTP server.